Cytophotometric DNA analyses were performed on 35 primary esophageal cancer. Histograms of DNA measurement were classified into three patterns (diploid pattern, aneuploid pattern and mosaic pattern) and were compared with histological findings, prognosis, and degree of lymphocytes infiltration around the tumor. Survival rate was worse in patients with mosaic pattern than the others, and 4-year survival rates of each patterns were 66.7% (diploid), 53.6% (aneuploid) and 25.4% (mosaic). Diploid cell line was observed frequently in the superficial cancers, and as the cancers infiltrated more deeply, mosaic cell line increased. Mosaic cell line appeared more frequently in well differentiated squamous cell carcinomas. In patients with mosaic pattern, there was high frequency of lymphnode metastasis and vascular invasion, as compared with diploid pattern. The rate of vascular invasion tended to increase in the following order; diploid, aneuploid and mosaic types. Furthermore in the diploid tumors, the degree of lymphocyte infiltration around tumor tended to increase. These findings suggest that the change of DNA content may occur frequently during tumor progression and may be affected by tumor infiltrating lymphocytes. So the DNA ploid pattern will be also to be one of the conjecturable factors of the prognosis of esophageal cancer.